U.S. patent number 5,353,639 [Application Number 08/063,742] was granted by the patent office on 1994-10-11 for method and apparatus for sizing multiple tubes.
This patent grant is currently assigned to Thermalex, Inc.. Invention is credited to James R. Brookins, James D. Gowan.
United States Patent |
5,353,639 |
Brookins , et al. |
October 11, 1994 |
Method and apparatus for sizing multiple tubes
Abstract
A sizing die for sizing a plurality of micro-extruded tubes has
a side fence, a clamping fence in substantial parallel relation
with and movable with respect to the side fence, a base fence
adjacent to and perpendicular to ends of the side fence and the
clamping fence, and a movable die platen for applying pressure to
the top of the stack of tubes. The side and base fences preferably
are fixed. The tubes to be sized are stacked on their sides against
the side fence with their internal webs aligned throughout. The
clamping fence and die platen are moved to be in mating engagement
with the stack. Pressure is applied through the die platen against
the top of the stack to compress the tubes to a desired
thickness.
Inventors: |
Brookins; James R. (Montgomery,
AL), Gowan; James D. (Montgomery, AL) |
Assignee: |
Thermalex, Inc. (Montgomery,
AL)
|
Family
ID: |
22051193 |
Appl.
No.: |
08/063,742 |
Filed: |
May 20, 1993 |
Current U.S.
Class: |
72/363;
72/370.23 |
Current CPC
Class: |
B21C
37/30 (20130101); B21D 53/06 (20130101); F28F
1/022 (20130101) |
Current International
Class: |
B21C
37/30 (20060101); B21C 37/06 (20060101); B21D
53/06 (20060101); B21D 53/02 (20060101); F28F
1/02 (20060101); B21C 037/30 () |
Field of
Search: |
;72/363,367
;29/890.053,890.054 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Larson; Lowell A.
Attorney, Agent or Firm: Mason, Fenwick & Lawrence
Claims
What is claimed is:
1. A method of sizing tubes, comprising the following steps:
providing a plurality of tubes having a predetermined length and
width, each of the tubes having a flattened oval cross-section, a
pair of substantially planar side surfaces, and at least one
internal longitudinal web extending therein perpendicular to the
planar side surfaces;
providing a sizing die having a box-like cavity for receiving the
tubes, the sizing die having a pair of parallel, spaced apart side
fences having inner surfaces extending at least the full length of
the sides of the tubes being sized, at least one of the side fences
being movable relative to the other side fence between and open
position and a closed position, and a base fence, the base fence
being disposed adjacent to and extending perpendicular to ends of
the side fences, the cavity being at least in part defined by the
inner surfaces of the side fences and the base fence;
stacking the tubes in a stack in the box-like cavity of the sizing
die between the side fences and aligning the internal webs of tubes
throughout the stack, the stack having a bottom end adjacent the
base fence and a top end opposite the bottom end;
moving the movable side fence toward the other side fence to fix
the tubes against lateral movement; and
applying pressure equally across the entire planar side surface of
the top end of the stack of tubes in a direction towards the base
fence, thereby sizing and flattening the tubes consistently and
evenly.
2. The method of forming tubing of claim 1, further comprising the
step of providing a movable die platen in parallel spaced relation
to the base fence, and wherein in said pressure-applying step, said
die platen is moved from an open position to a closed position to
provide pressure against the top end of the stack of tubes.
3. A sizing die for sizing tubes having substantially planar
opposed sides, comprising:
a side fence having a substantially planar inner surface extending
at least the full length of the tubes being sized;
a clamping fence in substantial parallel relation with said side
fence, said clamping fence having a substantially planar inner
surface extending at least the full length of the tubes being sized
and being movable relative to said side fence from an open position
to a closed position;
a base fence adjacent to and perpendicular to ends of said side
fence and said clamping fence, said base fence having an inner
surface, said inner surfaces of said side fence, said clamping
fence, and said base fence defining a cavity for receiving a
plurality of tubes stacked on their sides; and
a die platen for applying pressure to the top of the stack of
tubes, said die platen being in parallel spaced relation to said
base fence and movable between an open position and a closed
position, and said die platen having a mating surface for
contacting the top of the stack of tubes, said mating surface
having substantially the same dimensions as the sides of the tubes
being sized, whereby said mating surface will contact the entire
upper surface of the top of the stack of tubes.
4. The sizing die of claim 3, wherein said side fence is fixed.
5. The sizing die of claim 3, wherein said base fence is fixed.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to tube sizing devices, and more
particularly, to a method and apparatus for sizing flat,
multi-void, extruded tubes for automotive heat exchangers.
2. Description of the Invention
Conventional aluminum heat exchangers were manufactured with
relatively long pieces of multi-void tubing (i.e., tubing in which
the interior space is divided into multiple longitudinal voids by a
plurality of longitudinal webs), and then bent into a serpentine
configuration. Although these serpentine heat exchangers were
satisfactory with fluorocarbon refrigerants R-12 and R-22, they did
not perform well with CFC-134a.
A new configuration of condenser core thus was developed for use
with CFC-134a: the micro-multi-void extrusion. These
micro-extrusions (referred to herein as "micro-extruded tubes") are
cut to length and assembled to make up a series of parallel paths
for the refrigerant to flow through.
However, prior art extrusion technology originally could not
produce a tube with micro-multi-voids to the extremely tight
tolerances required in the manufacture of parallel-flow condenser
coils. The prior art thus developed tube sizing technology which
could control the thickness of the micro-extruded tubes. Currently,
there are two methods in use in the art. The first method is
rolling, in which the microtube is passed through a series of
rollers which reform the material to a pre-determined size. The
roller sizing machines which are used in the rolling method
generally are fed microtubes from a coil of material. The rolling
method is very slow and costly to perform.
U.S. Pat. No. 5,058,266 to Knoll is illustrative of the rolling
method. As disclosed by Knoll, the tubes as initially extruded have
an oval shape with two transverse webs connecting the long sides of
the oval. The tube is then rolled under pressure, flattening the
oval sides and comprising and bending the transverse webs. In
addition, there is disclosed a similar rolling operation for tubes
having one or two internal fins which initially do not extend
entirely to the far wall of the tube. However, upon rolling, the
two sides of the tube are flattened, and the internal fins do not
contact the far wall of the tube.
A second method in use in the art is a compression method, in which
a die is sized to hold a single tube. The tube is placed in the die
and compressed to reach the desired size. The compression method
also is very slow and costly to perform, because it treats only a
single tube at a time.
U.S. Pat. Nos. 3,776,018 and 3,662,582 to French are illustrative
of the compression method. As disclosed by French, heat exchanger
tubing of an oval cross section with two parallel opposite sides is
made by compressing tubes initially having a circular cross section
and short internal fins. The internal fins act as spacers to
prevent excessive compression of the tube. After the compression
step, the walls of the tube are partially separated by fluid
pressure.
Compression has also been used generally for sizing single tube
blanks, both for heat exchangers and other applications.
In U.S. Pat. Nos. 4,829,803 and 4,744,237 to Cudini, a box-like
frame member is formed by compressing a tube blank into a square
shape between two matching dies. Each die has a rectangular groove
in it, such that when the two dies are brought together they
compress a tube of circular or similar cross section into a
rectangular cross section shape.
In U.S. Pat. No. 4,527,411 to Shinosaki et al., the circular tube
is heated to a temperature of 550.degree. to 1250.degree. C. and
compressed within a box-like form having three sides by the
application of pressure through a compressing side.
In U.S. Pat. No. 4,204,309 to Lefrancois, a process of compressing
hollow bead rings for the beads of pneumatic tires. The beads have
an oval or diamond-shaped cross section, with a web extending from
one of the longer sides partially across the cross sectional
distance. The opposite wall of the tube may have a mating surface
into which the transverse webs fit at the end of the compression
step. However, no particular compression method is specified.
According to the above-discussed references, only one tube is sized
at a time in a die that has been designed to hold only one tube
during the application of the sizing pressure. Thus, the method is
also relatively slow and expensive. It is the solution to these and
others objects to which the present invention is directed.
SUMMARY OF THE INVENTION
Accordingly, it is a principle object of the present invention to
provide a method and apparatus for sizing a plurality of tubes, and
particularly micro-extruded tubes, at one time.
It is another object of the invention to provide a method and
apparatus for sizing multi-void, micro-extruded tubes suitable for
use in a parallel flow-type of heat exchanger, such as a condenser
coil.
It is a further object of the invention to provide an efficient and
less expensive method of making automotive heat exchangers.
To achieve these objects, a sizing die according to the present
invention is herein provided. The sizing die comprises a fixed side
fence and a movable clamping fence which is parallel to the fixed
side fence. A fixed base fence is disposed adjacent to ends of the
fixed side fence and the clamping fence, and extends perpendicular
to the fixed side fence and the clamping fence. A movable die
platen is positioned parallel to the fixed base fence and between
the fixed side fence and the movable clamping fence. The die platen
has a mating surface having substantially the same dimensions as a
side of the tube blanks to be sized.
Each of the micro-extruded tubes to be sized has a flattened oval
cross section, a pair of substantially planar side surfaces
disposed in parallel relation to each other, and at least one
internal web extending through the tube and perpendicular to the
planar side surfaces.
In the method according to the invention, a predetermined number of
micro-extruded tubes are stacked on the base fence between the
fixed side fence and the clamping fence. The internal webs of the
tubes are aligned throughout the stack, perpendicular to the plane
of the base fence. The clamping fence is moved toward the stack of
tubes to prevent the stack from moving laterally. The die platen is
moved toward the stack of tubes and the mating surface of the die
platen is in mating engagement with a side surface of the uppermost
tube in the stack. A predetermined amount of pressure is applied to
the stack of tubes through the die platen. The pressure is applied
equally across the entire side surface of the uppermost tube and is
transmitted equally through all the tubes of the stack in the
sizing die.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention is better understood by reading the following
Detailed Description of the Preferred Embodiments with reference to
the accompanying drawing figures, in which like reference numerals
refer to like elements throughout, and in which:
FIG. 1 is a perspective view of a sizing die in accordance with the
present invention, with the clamping fence and the die platen in
their open positions.
FIG. 2 is a perspective view of the sizing die of FIG. 1, with the
clamping fence being in the closed position to fix the tubes to be
sized against lateral movement.
FIG. 3 is a perspective view of the sizing die of FIG. 1, with the
clamping fence and the die platen being in their closed
positions.
FIG. 4 is a perspective view of a micro-extruded tube to be
sized.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In describing preferred embodiments of the present invention
illustrated in the drawings, specific terminology is employed for
the sake of clarity. However, the invention is not intended to be
limited to the specific terminology so selected, and it is to be
understood that each specific element includes all technical
equivalents which operate in a similar manner to accomplish a
similar purpose.
Referring particularly to the drawings, there is shown in FIGS. 1
through 3 an open sizing die 10 comprising die fences 12, 14, and
16, and die platen 18 which define a cavity 20 having an
approximately rectangular cross section throughout. Fixed side
fence 12 has a substantially planar inner surface 12a. Clamping
fence 14 is movable toward fixed side fence 12 and has a planar
inner surface 14a parallel to inner surface 12a of fixed side fence
12. Base fence 16 is disposed adjacent to ends of fixed side fence
12 and clamping fence 14. Inner surface 16a of base fence 16 is
perpendicular to inner surface 12a of fixed side fence 12 and inner
surface 14a of clamping fence 14. Die platen 18 has a mating
surface 18a parallel to inner surface 16a of base fence 16.
As best shown in FIG. 4, a micro-extruded tube 20 for sizing in die
10 has two substantially planar opposite side surfaces 30. The
dimensions of mating surface 18a of die platen 18 are substantially
the same as those of the side surfaces 30 of micro-extruded tubes
20 to be sized.
At least one internal web 32 projects inwardly from side surface 30
substantially perpendicular to side surfaces 30. Internal webs 32
are of the same height and are preferably equally spaced. Internal
webs 32 extend the full length of micro-extruded tube 20, so that
the interior of micro-extruded tube 20 is divided into individual
flow channels 34.
In use, micro-extruded tubes 20 are stacked in die 10 between fixed
side fence 12 and clamping fence 14, with the lowermost
micro-extruded tube resting on base fence 16. Internal webs 32 are
aligned throughout the whole stack, and are perpendicular to base
fence 16. Clamping fence 14 is moved towards fixed side fence 12 to
a position where inner surface 14a of clamping fence 14 is in
mating engagement with the stack of micro-extruded tubes 20.
Clamping fence 14 is fixed into position against the stack of
micro-extruded tubes 20 to prevent any lateral movement of
micro-extruded tubes 20 during the sizing operation.
Die platen 18 is then moved toward the stack of micro-extruded
tubes 20 so that its mating surface 18a is in mating engagement
with upper side surface 30 of the uppermost micro-extruded tube 20
in the stack. A predetermined amount of pressure is applied equally
across upper side surface 30 of the tube 20 at the top end of the
stack, and is transmitted equally throughout all micro-extruded
tubes 20 within sizing die 10 to cause all micro-extruded tubes 20
to be compressed equally, resulting in an equal reduction in the
thickness of all of micro-extruded tubes 20 (i.e., the dimension of
all of micro-extruded tubes 20 between side surfaces 30) and an
accompanying increase in the tube length.
Movement of die platen 18 to achieve the required pressure can be
achieved in any conventional manner, for example, through
hydraulic, pneumatic, mechanical or electrical means or any
combination of these means. These pressure applying procedures are
generally well known among those skilled in the art, and therefore
are not described in detail herein.
Because a plurality of micro-extruded tubes can be sized at the
same time by the sizing die, productivity is dramatically increased
compared with prior methods. Another advantage of this invention is
that the thickness of the extruded micro-extruded tubes can be
controlled by the amount of pressure applied. Thus, the extrusion
procedure produces the cross section illustrated to a very high
degree of accuracy, uniformity and repeatability.
Microtubes frequently are coated with a substance intended to
enhance or protect the properties of the base metal. This coating
causes the microtubes to have a rough, sandpaper-type texture,
which is undesirable. A further advantage of the method in
accordance with the invention is that the micro-extruded tubes
sized according to this invention have a smooth exterior surface
condition.
A further advantage of this invention is that the tubes produced by
the procedure according to this invention exhibit very small
amounts of core bow, thus reducing problems normally associated
with core bow during the core assembly process.
Although preferred embodiments of the present invention have been
described herein in detail, it would be appreciated by those
skilled in the art that various modifications and alterations can
be made to these embodiments without materially departing from the
novel teachings and advantages of this invention. For example, the
apparatus in accordance with the present invention can be used to
size tubes other than micro-extruded tubes in accordance with the
method of the present invention.
Accordingly, it is to be understood that all such modifications and
alterations are included within the scope of the invention as
defined by the following claims.
* * * * *